Feedback Control - Temperature & Other Vital Signs

Question 1

Commonly assessed vital signs (7)

Answer 1

Pulse
BP
Respiratory rate
O2 Saturation
Temperature
Consciousness
Capillary refill time

Question 2

Core Body Temp

Answer 2

Core Body & Outer shell
Homeostatically maintained at about 37.8 C

Normal - narrow range
Normothermia
Increased Body Temp
Overheating
Decreasing Body temp

Question 3

Sites for Monitoring Body Temp

Answer 3

Indirect estimate
- Ear drum
Direct estimate
- Rectal or oesophageal

Question 4

Normal Body Temp

Answer 4

Varies during day
May be altered by activity, exercise, emotions, etc
Menstrual cycle

Question 5

Heat Gain

Answer 5

Internal Environment –> Metabolic Heat Gain
External Environment –> Radiation, Convection and Conduction

Question 6

Heat Loss

Answer 6

External environment - Radiation, Convection and Conduction, Evaporation

Question 7

Internal heat gain - Metabolic Heat

Answer 7

Oxidation of metabolic fuel
Basal Metabolic Rate - increased hormones
Muscle activity
Shivering

Question 8

Radiation

Answer 8

Emission of heat energy
Human body emits and absorbs radiant heat
Half of Body’s heat loss through radiation

Question 9

Conduction

Answer 9

Transfer of heat between objects in contact
Heat moves from warmer to cooler
Depends on temperature gradient and thermal conductivity
Small percentage

Question 10

Convection

Answer 10

Transfer of heat energy by air currents that help carry heat away from body
Combines with conduction
Air next to skin warmed by conduction
Warmed air rises whilst cooler air falls
Forced air movement

Question 11

Evaporation

Answer 11

Energy is required to convert water in the skin surface and lining of respiratory airways into vapour
Passive evaporative heat loss occurs continuously = water molecules continuously passively diffuse from surface of skin and lining of respiratory airways
Sweating is an active evaporative heat loss (sympathetic NS)
Humidity

Question 12

Negative Feedback Control

Answer 12

Central/Peripheral Thermoreceptors –> Control centre in Hypothalamus –> Skeletal Muscle, Skin Arterioles, Sweat glands, behavioural adaptation

Question 13

Hypothalamus

Answer 13

Posterior centre –> COLD
Anterior centre –> Warmth

Connections with limbic system and cerebral cortex

Question 14

Posterior Hypothalamic Centre - COLD

Answer 14

Effectors
- Skin –> Vasoconstriction
- Skeletal Muscle –> Increased Muscle Tone, Shivering, Increased voluntary movement
Other behavioural adaptations - postural changes, warm clothing

Question 15

Anterior Hypothalamic Centre - WARMTH

Answer 15

Effectors
- Skin Arterioles –> Vasodilatation
- Sweat glands
- Skeletal muscles –> Decreased muscle tone, decreased voluntary movement
Other behavioural adaptations –> Cool clothing

Question 16

Fever

Answer 16

Set point raised
Chemical released from macrophages - endogenous pyrogen
Pyrogen stimiulate release of prostaglandins in hypothalamus
Prostaglands act on hypothalamic-thermos-regulatory centre to reset thermostat at higher temp
Hypothalamus initiate mechanisms to heat body cold response to raise body temp to new set point –> FEVER
Restoration - pyrogen release reduced or prostaglandin reduced
Cool the body mechanisms